1. Field of the Invention
The present invention relates to new wet-developable, bottom anti-reflective coatings formed using adamantyl monomers in the polymer and having excellent reflectivity control and good photoresist compatibility.
2. Description of Related Art
With the integrated circuit (IC) industry continuing to move to smaller feature sizes to increase information storage capabilities, outstanding anti-reflective techniques will be required to provide the needed critical dimension (CD)) control for 193-nm lithography. Bottom anti-reflective coatings will be the anti-reflective materials of choice for critical and even noncritical applications such as implant. Using a dyed resist with top anti-reflective coating will not be sufficient for 45-, 32-, and 22-nm node implant layers. The desired CD for implant for the 45-nm node is about 150 nm, and the desired CD for the 32- and 22-nm nodes for implant is about 130 nm.
While the bottom anti-reflective coatings being used for most present-day applications are plasma-developed (dry), the less-used developer-soluble (wet) bottom anti-reflective coatings offer certain advantages, including eliminating the reactive ion etching (RIE) step necessary for dry development, as well as the potential damage to plasma-sensitive layers in the stack. The exposed resist and developer-soluble bottom anti-reflective coating are removed in the same step using a photoresist developer (e.g., aqueous tetramethylammonium hydroxide (TMAH)). These developer-soluble anti-reflective coatings increase the etch budget by minimizing the removal of non-exposed resist during the bottom anti-reflective coating development step. However, developer-soluble bottom anti-reflective coatings do not always provide the resolution achievable with dry bottom anti-reflective coatings and are typically aimed at noncritical applications such as implant layers, where resolution requirements are not as severe.
Many different chemical platforms for preparing light-sensitive, positive-working, developer-soluble bottom anti-reflective coatings have been described before. These bottom anti-reflective coatings are usually thermosetting and include: a) a dye-filled bottom anti-reflective coating using a polymeric binder; b) a coating formed using acid-degradable hyperbranched polymers with polymer-bound chromophores; or c) a coating formed using dye-attached linear polymers. For these three highlighted approaches, the polymer films become solvent insoluble (crosslinked) during a hot plate bake step. Upon exposure to an appropriate light source and a subsequent post-exposure bake (PEB), they degrade to developer- or water-soluble materials. Nevertheless, the need still remains for bottom anti-reflective coating platforms with improved resolution and processing latitudes needed for critical microlithography applications.